The present invention relates to the treatment or repair of vasculature and more particularly, to delivering a graft device within a blood vessel to address vascular disease.
In recent years, there have been developments in the treatment or repair of the vasculature of humans or other living animals. These developments have been applied to various areas of vasculature to treat a number of conditions such as vessel weakening or narrowing due to disease. The methods developed have involved minimizing the invasive nature of repair so that patient morbidity and mortality can be reduced. The period of recovery has also been reduced with such advances.
Some people are prone to degeneration and dilatation of the aorta, leading to rupture and death from bleeding. A recently-developed method of arterial reconstruction involves the attachment of a tubular conduit (graft) to the non-dilated arteries above and below the degenerated segment using stents; hence the name xe2x80x9cstentgraftxe2x80x9d for the prosthesis. The lumen of the arterial tree is used as a conduit to the aorta; hence the name xe2x80x9cendovascular aneurysm repairxe2x80x9d for the procedure.
The procedure is relatively simple when the degenerated segment is without significant branches. The stent-graft needs only one lumen with an orifice at each end. But the procedure is much more complicated when the degenerated segment of the aorta contains branches, because the stent-graft also needs to branch and these branches need to be placed along multiple lines of insertion. The most common, and simplest, example is reconstruction of the aortic bifurcation. This technical hurdle was crossed relatively early. Yet there has been no significant progress in the intervening years towards reconstruction of areas with more branches, such as the suprarenal aorta, the aortic arch, or other complex vasculature near the kidneys or involving the hypogastric, iliac or femoral arteries. The main problem is that the branches are of variable size, variable orientation, and variable position. It is very difficult to create a graft that will mimic the native anatomy, and very difficult to place such a graft in exactly the right orientation and right position without causing ischemia of the vital organs that are fed by the aortic branches. This is especially true of the aortic arch, which has branches to the brain.
The aortic arch, for example, is affected by two degenerative processes, dissection and aneurysmal dilatation, that hitherto have been treated by open surgical reconstruction. The open surgical operation relies upon cardiopulmonary bypass, with or without hypothermic circulatory arrest. The associated mortality, morbidity, debility, pain and expense are all high.
Endovascular methods of reconstruction must deal with certain challenging anatomic features. For example, all three arteries that take origin from the aortic arch supply blood to the brain. Flow through these arteries cannot be interrupted for more than five minutes without risking irreversible neurologic damage. Moreover, the distribution of the arteries in any one patient, and the arch arteries, in particular, is highly variable. It is, therefore, not feasible to mimic this arrangement in every patient without very sophisticated reconstruction. Even if the graft matched the patient""s anatomy precisely, it would still be difficult to match the orientation and position of the branches of the graft to the branches of the native vasculature. Additionally, the arch arteries, for example, usually arise from the ascending portion of the arch at acute angles to the downstream aorta. Trans-femoral access to the arch arteries necessitates a sharp change of direction where these arteries arise from the aorta.
However, certain anatomic features lend themselves to endovascular repair. The aorta and in particular, the ascending aorta is long, straight and without significant branches. Further, the aorta is wide and consequently, there would be room for a main or primary graft conduit to lie alongside its branches. Also, it is relatively easy to gain access to the femoral and iliac arteries.
Accordingly, what is needed and heretofore unavailable is a system and method for treating or repairing complex vasculature while minimizing risk and the recovery time of the patient. The present invention meets these and other needs.
Briefly and in general terms, the present invention is directed to a device and method for treating or repairing diseased vasculature. The invention provides a minimally invasive approach to the treatment of complex vasculature characterized by a first vessel in fluid communication with a plurality of vessel portions extending at various angles from the first vessel. The present invention is also concerned with treating or repairing vessels which are difficult to access and which supply blood to vital organs which require a continuous source of blood and accordingly, avoids complexities associated with simultaneous insertion and deployment of multiple components.
The present invention embodies a graft device having a superior end, an inferior end, a midsection and a plurality of apertures. Each of the apertures of the grafting device are capable of being aligned with or placed in the relative vicinity of a vessel portion to enable an exterior component to extend from the grafting device to the vessel portion to enable an extension component to extend from the grafting device to the vessel portion. In one aspect, the superior and inferior ends of the graft device each include apertures and are configured within a first vessel portion and each of the apertures formed in the midsection are aligned with blood vessel portions extending at an angle from the first vessel. Further, it is contemplated that the graft device includes a main component and a plurality of extension components that are configured to mate with the main component. Various anchoring, mating and support structures are also contemplated that facilitate securing the graft device within vasculature for accomplishing repairing complex vessel anatomy. Occlusion structures are also included that can be used to close off one or more unused graft device apertures.
Additionally, the present invention embodies a delivery catheter system and method that accomplishes the deployment and attachment of the graft device within vasculature. The delivery catheter system includes structure for receiving the various components of the graft device of the present invention as well as a series of guidewires which provide a path taken by components of the delivery catheter system.
It is contemplated that a branched stent-graft of the present invention be constructed in-situ from multiple components, a main or primary stent-graft with multiple short branches and several branch extensions. Variations in arterial anatomy are accommodated intraoperatively through the independent selection of components as indicated by intraoperative measurements.
In one aspect, the device does not attempt to mimic native anatomy. For example, the widest portion of the primary stent-graft is attached (usually with a stent or an anchoring device) to the proximal aorta. All branches of the primary stent-graft originate at a level proximal to the branches of the aorta. The variable gap between branches of the stent-graft and branches of the aorta is accommodated by variation in the length of the extensions. Thus, several extensions run next to one another through the proximal aortic segment. This is possible because the central section of the primary stent-graft is sized to be much smaller than the native aorta in the region of the aortic branches. The space around the central section also allows for blood flow from the stent-graft branches to the aortic branches and continuing perfusion of the vital organs while extensions are added one by one. A distal aortic seal is established through a slightly wider segment. Alternatively, additional components can be added with their own branches to permit extension into other aortic branches, such as the iliac arteries.
The extensions can be filly-stented (lined from one end to the other with stents or some other means of support), yet flexible. As so configured, they maintain a stable position through a combination of stent support and anchoring or attachment mechanisms at both ends.
The two main sites requiring this kind of treatment are the aortic arch and the suprarenal aorta. The present invention also has applications in other complex anatomy including the iliac, hypogastric or femoral arteries. Although the principles are the same for such sites, differences in anatomy necessitate differences in basic technique. For example, in the arch, the extensions are introduced through the branch arteries, while in the suprarenal aorta the extensions are introduced through the stent-graft from a point of peripheral arterial access in the upper body, usually the left upper limb.
In a preferred embodiment of the present invention, the trunk of the primary stent-graft is bone-shaped with three segments; a narrow central segment and wider segments at both ends. The wider segments are large enough to engage the aorta. Typical diameters are 3.5-4.5 cm proximally and 2.5-3.5 cm distally. The central segment is smaller (approx. 2 cm). Three stent-graft limbs or branches arise from the transition zone between the proximal and middle segments. These are also small (approx. 1 cm). Their origins are staggered at 1 cm intervals both down the length of the trunk and around its circumference.
In one embodiment, there is a self-expanding anchoring device or stent in each of the five stent-graft orifices. Flexible bracing wires run along the outer aspect of the stent-graft between all five stents, so that each segment of the stent-graft is held to a fixed length. Guidewires run alongside the central catheter of the delivery system and through the stent-graft, entering through an inferior or distal orifice and exiting through the orifices of the branches to run back down the outer aspect of the stent-graft. At the base of each branch of the stent-graft there are several circumferential suture loops that form part of a stent-graft to stent-graft mating or attachment system.
Long, flexible, narrow, fully-stented stent-graft extensions exist in a range of lengths and diameters. Each has an external grappling mechanism on the outer aspect of the graft near the proximal tip. The inner 2-3 cm of the extension is sized to match the diameter of the primary stent-graft branch (approx. 1 cm). The rest of the extension is sized to match the diameter of the arch artery.
The stent-graft is inserted through a flexible sheath into the arch of the aorta from an access point in the femoral artery. When released from its sheath, the stent-graft expands. A catheter is advanced over one of the guidewires, through the trunk of the stent-graft and out of one of the branches. The guidewire is then withdrawn and directed into a waiting snare that was previously inserted into the aorta through corresponding arch artery. The distal stent-graft branch corresponds to the left subclavian artery, the middle stent-graft branch corresponds to the left carotid artery and the proximal stent-graft branch corresponds to the innominate (brachiocephalic) artery.
The femoro-brachial guidewires are used to insert calibrated catheters into the proximal aorta through the stent-graft branches. Angiography through the calibrated catheter allows the selection of a suitably sized extension. Each calibrated catheter is then exchanged (over the wire) for the delivery systems of the corresponding stent-graft extension. The extension is deployed within the stent-graft branch where it is secured by the friction generated by the outward pressure of its stents and by the interaction of the grappling mechanism with the loops of the stent-graft branch.
In other embodiments, the application of the present invention relates to treating complex vasculature involving the iliac, femoral, and hypogastric arteries. Various approaches are contemplated to accomplish the in-situ assembly of components of the graft device of the present invention.
Other components of the present invention include employing stents with a very high expansion ratio which are flexible and have a low profile. Various methods of accomplishing secure stent-graft to stent-graft attachment are also contemplated as are various methods of providing a graft component with a desired flexibility and radial strength.
These and other objects and advantages of the invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings of illustrative embodiments.